Roof bolt



ROOF BOLT 2 Sheets-Sheet 1 INVENTOR ATTORNEY a 2 M a 8. F/ 3W 7 Wm- 4 WWW M June 5, 1956 w. EDWARDS Filed Nov. 4, 1952 June 5, 1956 w. EDWARDS ROOF BOLT 2 Sheets-Sheet 2 Filed Nov. 4, 1952 INVENTUR LEW/8 WEDWA/EDS,

BY DMLQ E $T ATTURNFY ROOF BOLT Lewis W. Edwards, Coatesville, Pa., assignor to 'Lukens Steel Company, Coatesville, Pa., a. corporation of Pennsylvania Application November 4, 1952, Serial No. 318,610

4 Claims. (Cl. 72-105) This invention generally relates to a bolt of the expansion type and particularly to an expansion bolt for use in connection with bolting mine roofs and the like.

As is well known, mine roof bolting has in the past minimized the possibility of accidents in the mine. Also, mine roofs which are provided with bolts at. spaced intervals tend to make working conditions better and increase production and are instrumental in simplifying ventilation of the mine.

Prior art devices of this type, i. e., expansion bolts particularly adapted for mine roof bolting, generally depend a great deal for efficiency on the length and size of the hole drilled in the roof where the bolt is to beinstalled. Also, many roof bolts now in use have several thread portions which are subject to injury such as, for example, during the hammering operation in installing the bolt. Still further, bolts now in use, when installed, often have sharp edges protruding from the mine roof which obviously is hazardous. The invention to be hereinafter described overcomes the above difliculties, as'w'ell as several' other disadvantages common to the majority of bolts now in use.

Accordingly, it is the primary object of this invention to provide an expansion bolt especially adapted for use in connection with bolting the roof of a mine or the like and which is composed of a minimum number of parts, which is simple and quick to install, and that is durable and efiicient in action, and inexpensive to manufacture.

Another object of this invention is to provide a. roof bolt primarily for use in a mine, said bolt being constructed in such a manner that the length of the hole in the mine roof is of no particular importance as long as it is greater than the length of the bolt and wherein no protrusions having sharp edges extend from the roof after the bolt is in place, and wherein said bolt has nothreads adapted to be broken or injured.

Yet another object of this invention is to provide an expansion bolt particularly adapted for mine roofbolting having a plurality of locking means, thus insuring against the possibility of accidental release of the device once it is installed.

Other objects of this invention will become apparent in light of the following detailed description, wherein:

Figure 1 is a side view of the device, partly in section and showing the device partially entering the hole of a roof or the like;

Figure 2 is a view similar to Figure l but showing the device in its final position in the hole of the roof or the like;

Figure 3 is a sectional view' taken along the line 33 of Figure 2;

Figure 4 is a sectional view taken along the line 4-4 of Figure l;

' Figure 5 is an elevational view of the flat side'of the shank portion of the bolt;

Figure 6 is an elevational view of the flat side of the locking part of the bolt;

2,748,594 Patented June 5, 1956 Figure 7 is a sectional view taken along the line 7-7 of Figure 2;

Figure 8 is a rear plan view of the support used wit this device; and

Figure 9' is a sectional view taken along the line 99 of Figure 8.

Broadly, this invention provides means for bolting the roof of a mine or the like comprising a bolt preferably longitudinally divided into a main shank part and a locking part, the shank part tapering outwardly adjacent the head end to the inner end whereby, during the'inserting operation, the fiat face of the locking part rides over the flat face of the shank part, expanding, in wedge-like fashion, both parts transversely within the hole of the mine roof to provide a tight secure fit and lock in the hole of the bolt parts. The fiat face of the locking part is provided with a recess for the reception of a portion of the innermost part of the flat face of the shank member whereby further locking of the bolt parts, in addition to the wedging action, is provided. The heads of each bolt part are adapted to engage a roof plate member, said member being arch-shaped and having strengthening ribs provided on the exterior surface thereof and functioning to further lock the parts in position.

Referring to the drawing in detail, the numeral 1 generally represents the entire device comprising the support and both bolt parts. The bolt is preferably longitudinally divided into two sections, namely, a main shank part 2 and a. locking part 3, both of these parts having smooth head portions 4.

Specifically referring to Figures 1, 2, 3, 5 and 7, shank part 2 is substantially semi-circular or hemispherical in cross section from the head portion 4 to adjacent the hump or protrusion 5. The purpose of this laterally projecting rib or hump 5 is to form a fulcrum when the inner end of the shank portion is expanded and it is to be noted that efficiency in expansion is increased due tothe weakened. portion shown at 6 in the form of a depression in the outer surface immediately above the hump 5. From adjacent the hump 5 and the weakened area 6, the flat face 7 tapers outwardly toward the inner end of the shank portion and portions or parts 9 of the side of the shank portion 2 taper inwardly toward the inner end whereby the inner end of shank portion 2 is substantially sector-shaped or substantially of truncated sector shape in cross section, as is clearly shown in Figure 3. Also from adjacent the hump 5 to the inner end the shank part is similarly shaped in cross section although gradually reduced in size. It is to be noted that the section of the semi-circular cross section remaining at the inner end is provided with serrations, dimples, rings, or the like 8, to increase the surface friction for retaining the two parts in the hole, as shown in Figure 2.

From the head portion 4 to the inner end, the locking member 3 is substantially semi-circular in cross section and, of course, the inner face 11, as shown in Figure 6, is substantially flat throughout. Adjacent the inner end of the locking member 3, there is provided, as shown in Figures 3, 4 and 6, a recess 12, the purpose of which will be hereinafter described. This recess 12 preferably tapers upwardly as shown, although it is not essential that such a taper be provided. The surface of the locking member 11 at its tip and top at the inner end thereof is also tapered as shown clearly at 13 and 14 in Figures 1 and 2.

Referring to Figures 1, 2, 8 and 9 in particular, there is shown a yieldable spring-like roof supporting plate or member generally represented by the numeral 20. Preferably, the supporting plate is in the shape of a square, although circular or other shape would be satisfactory, and as shown in Figure l, is slightly bowed or arched in its original form. A hole for the reception of both bolt parts is provided in the member at 23 and for strengthening and rigidity purposes, the mem ber has a plurality of ribs 24, preferably in the form of an X pattern, as shown clearly in Figure 8.

In use, a hole 30 is made in the roof 22 of a mine or the like and the length of the hole is of no particular importance to efficient operation, as long as it is greater than the length of the bolt When in its final position. Thereafter, the shank member 2 is passed through the opening 23 in the support 20 and into the hole 30 and the support and shank member 2 appear as shown in Figure 1 with the support ends 21 engaging or abutting the roof surface 22. Locking member 3 is then passed through opening 23 in the support member and manually positioned in the hole 30 until it reaches a position as shown in Figure 1. It is to be understood, of course, that the true length of locking member 3 is more properly shown in Figure 2 than in Figure 1, and that throughout the drawing, the thickness of support member 20 has been exaggerated.

The fiat surfaces 7 and 11 are at this time abutting as shown in Figure 1. Thereafter, by hammering, a pneumatic hammer or other suitable means may be used, the head 4 of locking member 2, the flat surface 11 rides or travels over the outwardly tapered flat surface 7 of shank member 2, commencing a wedging action. This operation continues until, for example, the top 14 travels to a point about three-fourths the way up from the distance shown in Figure l and, during this travel, the part of the shank member above the fulcrum 4 is expanded to the left and the locking member 3 is expanded to the right. In this connection, it is recalled that the fulcrum point 5 and weakened portion 6 assist in simplifying expansion.

During initial expansion and wedging action, serrations 8 will commence to grip the side wall of the opening 30 and the outer surface of the locking member 3 will likewise be forced against the surface of opening 30. In this connection, it is to be noted that the taper 13 prevents excessive gripping or indentation in the surface of the hole 30 by member 3 which would be faulty and possibly prevent correctly positioning the parts. In other words, taper 13 acts as a sliding fulcrum point.

Continued hammering on head 4 further expands the parts and increases the travel upwardly of locking member 3. At some selected point, depending upon the size of recess 12 and the width of the taper 7 adjacent the inner end of the shank member 2, the taper 7 will snap into the recess 12 and ride therein. Continued upward movement will follow and the wedging and expanding action will also continue until the complete bolt is in a position such as that shown in Figure 2. Actually there will also be a slight bending of the inner portion of locking member 3, following the snapping action, as shown in exaggerated form in Figure 2.

During the final travel of locking member 3, the springlike member 20, which is yieldable, will be forced inwardly. The showing in Figure 2 of the support member 20 is supposed to represent the final position but it is to be understood that, depending upon the yielding characteristics thereof, a position whereby the interior of the member is more flush with the roof surface than illustrated may be obtained. Depending upon the thickness and flexibility of support member 20, there will be a deforming of this member during final inward movement thereof, such that a spring action results with a reactive force against the bolt heads. Also, the final degree of deformation of the member 20 serves as a warning as to whether or not the bolt is completely expanded in the hole. Furthermore, the ribs, preferably in the form of an X pattern, increase the rigidity and strength of the entire device and, of course, the member functions as a support for the roof 22.

Again referring to the recess 12, the purpose of this is not only to form an accurate guide at the end of the locking structure, thus preventing any torsional roll of shank member 2, but to furnish an additional locking means for securing the bolt in place. For example, it would be very difficult for the tapered part of face 7 to snap out of recess 12. In addition to this as a locking means, of course, the serrations 27 on the bolt heads provide a locking effect as do the serrations 8 and the wedge-like action adjacent taper 13.

The above description and drawings disclose a single embodiment of the invention as specific language has been employed in describing the several figures. It will nevertheless be understood that no limitations of the scope of the invention are thereby contemplated, and that various alterations and modifications may be made such as would occur to one skilled in the art to which the invention relates.

Having thus described the invention, what I claim as new, and what is desired to be secured by Letters Patent is:

1. An anchor bolt consisting of an elongated shank part and a cooperating complementary elongated locking part, said parts having a head at a corresponding end thereof, each of said parts being semi-circular in cross section from the headed end to a point along the length thereof spaced from the headed end and each of said parts having cooperating flat faces, the flat face on the shank part tapering in width from said point to the end remote from said head and the thickness of said shank between the flat face and the diametrically opposite surface progressively increasing from said point to said remote end, the remote end of said shank part thus being substantially of truncated sector shape in cross section, said locking part being of substantially uniform cross sectional shape from the headed end to a point adjacent to but spaced from the remote end, the section of said locking part from said point thereon to the remote end having a semi-circular recess in the fiat face thereof, said recess receiving a portion of the tapering fiat face of said shank part.

2. An anchor bolt as recited in claim 1 and further including a laterally projecting rib positioned on the curved surface of the shank part at said point thereon and a depression in the curved surface of the shank part immediately adjacent to said rib and positioned on the side of said rib opposed to the headed end, whereby said rib acts as a fulcrum and the depression as a weakened point to facilitate bending of the shank part at said rib and depression.

3. An anchor bolt as recited in claim 1 wherein a section of the locking part extending from adjacent the remote end to the remote end progressively decreases in thickness.

4. The anchor bolt of claim 1 wherein said recess progressively increases in size from said point on the locking part to the remote end thereof.

References Cited in the file of this patent UNITED STATES PATENTS 551,043 Otto Dec. 10, 1895 741,563 Stevens et al Oct. 13, 1903 780,960 Palmer Jan. 24, 1905 1,016,798 Thomson Feb. 6, 1912 1,025,275 Kennedy May 7, 1912 1,116,710 Keller Nov. 10, 1914 1,248,003 Pleister Nov. 27, 1917 1,850,768 Peirce Mar. 22, 1932 2,398,130 Beijl Apr. 9, 1946 

